This invention relates to lightweight steel frame construction for residential and commercial buildings, and in particular, this invention is directed to a lightweight steel frame system having end nailed shear connections where lightweight steel structural members frame into support members.
A long history has developed certain accepted framing practices for constructing wood structures. For example, wood roof truss systems are widely used throughout the framing industry because such systems simplify roof construction, and enable contractors to place a structure in progress under the protection of a roof more quickly. Additionally, a well designed roof truss system will, 1) reduce the need for inside bearing walls, 2) provide long spans that create large open interior spaces, and 3) reduce on-site labor costs associated with conventional rafter and joist roof frame type construction. Suppliers and designers typically manufacture roof truss systems from either solid wood and/or laminated materials, and more recently, such roof truss systems are manufactured with lightweight steel materials. In traditional wood framing, where wooden roof truss systems replace rafter and joist stick framing, designers recognize that certain framing connections are difficult to make due to the structural properties inherent in wood materials. For example, in a roof design where it is necessary to frame a series of wood roof truss members directly into a wood girder truss or support member, a shear connection is used. It is impractical to make such shear connections by driving fasteners through the support member and directly into the end grain of the roof truss (defined herein as "end nailing"). This is because end nailed shear connections in wood materials produce weak connections that will fail under load conditions. Therefore, framers have found that it is necessary to use connection hardware that enables a builder to direct nail the shear connections that attaches wood roof truss members to a support member. Direct nailing is defined in the "Glossary of Terms" published by the Wood Truss Council of America, as nailing (fastening) perpendicular to the member being nailed. Direct nailing practice has produced an vast array of various shaped connection hardware products that range from special hangers and angles to clips and other devices. Such connection hardware is very troublesome in the field and from a design viewpoint. To illustrate, clips and hangers complicate the load path from the roof truss to the foundation of the structure. The forces associated with such hanger connections are unpredictable and difficult to calculate. In the field, connection hardware adds extra framing parts, and increases labor costs.
Similar problems arise where builders use lightweight steel to frame an entire structure. In such instances, floor joists that shear connect into support members and walls and girders present the same framing problems as described above for roof truss systems. Likewise, where lightweight steel headers span openings such as doorways, windows, arches and the like, connection hardware must be used as heretofore described for the connections. Therefore, there is a long felt need within the construction industry to eliminate the need for using connection hardware when shear connecting roof truss members, joists, or headers that frame into support members such as girders and walls or the like.